I'm going to have to purchase a library card for the next county over once she finishes all the books in our system.

Many (most?) local libraries will acquire any book you ask for, as long as it fits within their acquisitions policy, which usually covers all novels, for example. They can also do inter-library loans (ILL), usually for free. So it may not be necessary to switch libraries just yet. Besides, the other library's collection is probably very similar to your current one.